ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Optical emission characteristics of vacuum ultraviolet (VUV) light from large area (≈50 cm2) electrical gas discharges were investigated in order to develop a windowless photochemical vapor deposition (photo-CVD) reactor and to prepare silicon-based thin films at low temperature (≈300 °C). The electrodes configuration is such that the ions impact upon the substrate is strongly minimized. Among the four investigated gases (He, Ar, H2, and N2), argon is the best candidate because it provides the more monochromatic VUV light (121.5 nm) which corresponds well to the maximum of the silane and disilane photoabsorption curves. Emission spectra of the photo-CVD induced in argon–silane mixtures clearly give evidence of the formation of molecular hydrogen and of Si* excited atoms and, indirectly, the part played by low hydrogen content radicals (namely, SiH). The deposition rate of hydrogenated amorphous silicon films obtained by windowless photo-CVD using this strong emission band at 121.5 nm is proportional to the SiH4 and Si2H6 contents in argon up to 20% and 6%, respectively. The deposited films present a low average hydrogen concentration value of less than 10% and smooth surfaces (〈20 A(ring)) for silicon hydride gas partial pressures lower than 15%. Over this value, the deposits become very rough ((approximately-greater-than)500 A(ring)), due to SiHn clusters formation in the gas phase. Finally, low temperature growth of silicon nitride films by the VUV dissociation of silane and/or disilane–nitrogen mixtures is demonstrated. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.361150
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